This invention relates to a power transmission belt and method for fabricating the same, and particularly relates to a power transmission belt such as a V-ribbed belt or a V-belt in which short aramid fibers and non-aramid synthetic fibers are mixed into its compression rubber and a method for fabricating the same.
As disclosed in Japanese Patent Application Laid-Open Gazettes Nos. 3-219147 and 7-4470, there are conventionally known power transmission belts in which a crowd of short fibers are mixed into their compression rubber in a manner to be oriented along the width of the belt and some of the short fibers are extruded from the surface of the compression rubber. Power transmission belts of such kind aim at enhancing bearing strengths and wearing properties of their friction drive sections and preventing noise production during their running.
However, even such a power transmission belt out of which some of the short fibers extrude, if the total area of extruded sections of the short fibers occupying the surface of the compression rubber is small, cannot enhance its wearing property so much because the area of the compression rubber in direct contact with a pulley becomes correspondingly large.
For the purpose of increasing the exposure areas of short fibers with respect to the surface area of the compression rubber, Japanese Patent Application Laid-Open Gazette No. 1-164839 has proposed a power transmission belt as shown in FIG. 14. In this power transmission belt, extruded sections 102 of short aramid fibers 101 mixed into a compression rubber 100 are 0.065 to 0.13 mm long, longer than those of conventional short fibers, and are bent in a particular direction 103 along a working flank of the belt.
In such a power transmission belt, though the exposure areas of short fibers 101 can be increased, the extruded sections 102 are bent at their roots and therefore made substantially flush with the surface of the compression rubber 100. Accordingly, the extruded sections 102 are difficult to together form surface unevenness as considered as effectively suppressing noise. This invites a problem that the effect of suppressing noise cannot sufficiently be obtained.
Furthermore, since the extruded sections 102 of short fibers are bent in the particular direction 103 along the surface of the compression rubber 100, running the belt in a reverse direction would largely change properties of the belt. Therefore, in order for the belt to obtain its properties as designed, the belt must be checked carefully on its running direction at the time of fitting to pulleys. In addition, this conventional belt cannot sufficiently exhibit its performance when used with devices capable of conveniently switching the running directions of the belt.
Moreover, if the length for which the short fiber is extruded from the surface of the compression rubber 100 is too large, the belt will largely change its properties when the extruded sections 102 are reduced by abrasion. Therefore, considering to maintain desired belt properties constant for a long time, there is a limit to increasing the extruded length of the short fiber. Accordingly, it has been desired to make great strides in enhancing the performance of the belt by improving not only short fibers but also the compression rubber 100.
In view of these problems, an object of the present invention is to provide a power transmission belt excellent in wearing property, hard to produce noise and independent of its running direction.
Another object of the present invention is to further enhance the performance of the belt by improving the surface configuration of the compression rubber.
To attain the above first object, a power transmission belt of the present invention is constructed so that at least two types of crowds of short fibers, namely, a crowd of short aramid fibers and a crowd of non-aramid synthetic fibers, are mixed into a compression rubber and these crowds of short fibers are improved in configuration extruded out of the compression rubber.
More specifically, a power transmission belt of the present invention is directed to a power transmission belt in which a crowd of short aramid fibers and a crowd of non-aramid synthetic fibers are mixed into a compression rubber thereof in a manner to be oriented in a given direction and some of the short aramid fibers and some of the non-aramid synthetic fibers each have an extruded section extruded from a surface of the compression rubber, and is characterized in that the extruded sections of the non-aramid synthetic fibers are inclined in a given direction, the extruded sections of the short aramid fibers are inclined in multiple directions and the extruded section of the short aramid fiber is longer than the extruded section of the non-aramid synthetic fiber.
With this construction, since both the short aramid fibers and the non-aramid synthetic fibers are extruded from the surface of the compression rubber, the total exposure area of these two types of short fibers is large. Accordingly, the belt can enhance wearing property. Further, since some of the short aramid fibers are extruded in a manner to be inclined in multiple directions, the wearing property of the belt can be enhanced substantially uniformly in every direction. Therefore, the belt decreases the dependency on its running direction. Accordingly, the belt can enhance bearing strength and wearing property in either running direction. Furthermore, the short aramid fiber is more resistant to wear than the non-aramid synthetic fiber because of its relatively high strength. Therefore, even if the extruded section of the short aramid fiber is longer than that of the non-aramid synthetic fiber, the extruded section of the short aramid fiber is not rapidly reduced in length by abrasion. Accordingly, the belt does not change performance for a long time. Moreover, since the extruded sections of both the short aramid fiber and the non-aramid synthetic fiber are different in the lengths, microscopic unevenness is formed above the surface of the compression rubber. This microscopic unevenness can suppress the occurrence of noise.
The extruded sections of both the short aramid fibers and the non-aramid synthetic fibers are preferably raised from the surface of the compression rubber.
With this construction, the extruded sections of both the short aramid fibers and the non-aramid synthetic fibers have their root portions raised up from the surface of the compression rubber without falling to it. Accordingly, microscopic unevenness is formed over the surface of the compression rubber so that the root portion of each extruded short fiber constitutes a microscopic convexity and a surface region adjoining a place where each extruded short fiber is implanted constitutes a microscopic concavity, thereby suppressing the occurrence of noise.
The extruded section of the short aramid fiber is preferably bowed.
With this construction, the extruded sections of the short aramid fibers have sufficiently large exposure areas with respect to the surface area of the compression rubber, resulting in enhanced wearing property of the belt.
The extruded section of the short aramid fiber is preferably bowed first in one direction and then another direction on the way from root to tip thereof.
With this construction, since the extruded sections of the short aramid fibers are formed in curled shape, they exert restoring forces like leaf springs on a pulley. As a result, the extruded sections of the short aramid fibers can absorb variations in belt tension associated with the running of the belt. Also, stresses placed on the root portions of the extruded short aramid fibers can be relaxed by the restoring forces of the extruded sections of the short aramid fibers. Accordingly, the short aramid fibers can be prevented from dropping out of the compression rubber.
The extruded sections of the non-aramid synthetic fibers are preferably plastically deformed into flat shape.
With this construction, since the extruded sections of the non-aramid synthetic fibers are plastically deformed, they are not melted and can maintain their strengths intrinsic in synthetic fibers. Further, since the extruded sections of the non-aramid synthetic fibers are formed into flat shape, the surface area of each extruded fiber can be increased thereby further enhancing the wearing property of the belt.
The extruded section of the non-aramid synthetic fiber is preferably formed in a sector gradually broadened toward a distal end thereof.
With this construction, the extruded section of the non-aramid synthetic fiber can obtain a specific flat configuration of large exposure area.
If the extruded sections of short fibers are shortened by abrasion, the belt will change its properties. Therefore, excessively long extruded sections of short fibers could increase changes of the belt properties with time and make the belt difficult to exhibit constant performance for a long time. Accordingly, the extruded section of the short aramid fiber is preferably 50 xcexcm or smaller in length and the extruded section of the non-aramid synthetic fiber is preferably 30 xcexcm or smaller in length.
With this construction, the extruded section of each short fiber can obtain a suitable configuration of small change with time.
To attain the above second object, a power transmission belt of the present invention is so constructed that unevenness is provided in the surface of the compression rubber to increase its entire surface area.
Specifically, in the power transmission belt, the surface of the compression rubber is preferably formed in uneven configuration.
With this construction, since the surface of the compression rubber is formed unevenly, its entire surface area can be increased. This enhances the performance of the belt. In addition, clearances are likely to be formed between contact surfaces of the belt and a pulley. Accordingly, even if water or the like enters between the belt and pulley, it can be distributed or discharged through the clearances, which stabilizes frictional resistance of the belt.
The surface unevenness of the compression rubber is preferably formed in wavy shape. Thereby, a suitable uneven configuration can be formed in the surface of the compression rubber.
The surface unevenness of the compression rubber is preferably formed to have a level difference of 0.5 to 10 xcexcm. Also in this case, a suitable uneven configuration can be formed in the surface of the compression rubber.
A method for fabricating a power transmission belt of the present invention is directed to a method for fabricating a power transmission belt in which some of a crowd of short aramid fibers and some of a crowd of non-aramid synthetic fibers are extruded from a surface of a compression rubber, and is characterized by comprising the step of grinding the compression rubber into which the crowd of short aramid fibers and the crowd of non-aramid synthetic fibers are mixed in a manner to be oriented in a given direction with a grinding wheel having super abrasives extruded for 50 to 95% in grain size thereof from the surface of the grinding wheel.
According to this method, since the height of extrusion of each of the super abrasives is large, the short aramid fibers and the non-aramid synthetic fibers can be easily extruded from the surface of the compression rubber. Further, since the short aramid fiber has greater strength and elasticity over the non-aramid synthetic fiber, the extruded sections of the non-aramid synthetic fibers are extruded in a manner to be inclined in a single direction, whereas the extruded sections of the short aramid fibers are extruded at greater lengths in a manner to be inclined in multiple directions. In addition, such a large height of extrusion of the super abrasive can facilitate to form the surface of the compression rubber into uneven configuration.
Another method for fabricating a power transmission belt of the present invention is also directed to a method for fabricating a power transmission belt in which some of a crowd of short aramid fibers and some of a crowd of non-aramid synthetic fibers are extruded from a surface of a compression rubber, and is characterized by comprising the step of grinding the compression rubber into which the crowd of short aramid fibers and the crowd of non-aramid synthetic fibers are mixed in a manner to be oriented in a given direction with a grinding wheel having super abrasives the density of which is 3.5 to 55%.
According to this method, since the density of the super abrasives is relatively low, the short aramid fibers and the non-aramid synthetic fibers can be easily extruded from the surface of the compression rubber. Further, since the short aramid fiber has greater strength and elasticity over the non-aramid synthetic fiber, the extruded sections of the non-aramid synthetic fibers are inclined in a single direction, whereas the extruded sections of the short aramid fibers are inclined in multiple directions and extruded at greater lengths. In addition, such a small density of the super abrasives can facilitate to form the surface of the compression rubber into uneven configuration.
Still another method for fabricating a power transmission belt of the present invention is also directed to a method for fabricating a power transmission belt in which some of a crowd of short aramid fibers and some of a crowd of non-aramid synthetic fibers are extruded from a surface of a compression rubber, and is characterized by comprising the step of grinding the compression rubber into which the crowd of short aramid fibers and the crowd of non-aramid synthetic fibers are mixed in a manner to be oriented in a given direction with a grinding wheel having super abrasives which are each extruded for 50 to 95% of grain size thereof from the surface of the grinding wheel and the density of which is 3.5 to 55%.
According to this method, since the height of extrusion of each of the super abrasives is large and the density thereof is relatively low, the short aramid fibers and the non-aramid synthetic fibers can be extruded with great ease from the surface of the compression rubber. Further, since the short aramid fiber has greater strength and elasticity over the non-aramid synthetic fiber, the extruded sections of the non-aramid synthetic fibers are inclined in a single direction, whereas the extruded sections of the short aramid fibers are inclined in multiple directions and extruded at greater lengths. In addition, the surface of the compression rubber can be very easily formed into uneven configuration.